Saturday, November 05, 2005

Lessons in Cat Genetics, Part One: Siamese Cats

Sometimes science is fun. Example: the genes that control cat coat color.

Here is a really simplified way of thinking about cat color:

Colorless stuff --Gene C--> Black pigment --Gene O--> Orange pigment

To get past the first arrow (to make Black pigment), you have to have a functioning copy of Gene C. To get past the second arrow (to make Orange pigment), you have to have a functioning copy of Gene O.

Orange cats have at least one functioning copy of Gene C, so they can get past the first arrow. They also have at least one functioning copy of Gene O, so they can get past the second arrow. If you have an orange cat, congratulations!

Colorless stuff --Gene C--> Black pigment --Gene O--> Orange pigment


Black cats have at least one functional copy of the Gene C. But they can go no further, because they have no functional Gene O. Their pigment gets stuck at black. This is warmfuzzy's cat.

Colorless stuff --Gene C--> Black pigment




White cats (100% white, with pink eyes) have two nonfunctional copies of Gene C. They might have a good copy of Gene O, but there is no way to tell, because they can’t even get past the first arrow. [note: this is really rare; most white cats have colored eyes and have white fur for a different reason]

Colorless stuff




Siamese cats have a weird, semi-functional version of the Gene C. They can make black pigment, but not very well. Their Gene C has a mutation that causes the product of Gene C to stop working at high temperatures. The result? In the colder areas of the cat’s body, the cat can get past the first arrow. In the warmer areas, it can’t. So you end up with a cat that looks like this one. The cold areas (feet, tail, nose, ears) are black, and the warmer areas are not. (This cat also has a nonfunctional Gene O, so it can't make orange.)

Colorless stuff --Gene C, working in cold areas--> Black pigment in cold areas

True story.

6 comments:

warm fuzzy said...

Let's hear it for Cat Genetics!

What about calico cats? They are orange, black, and white-- how does that work?

nell said...

And how come they gots spots?

scarlet panda said...

Trust me, all of your questions will be answered in due time. Calico cats are a pretty advanced topic. You need to understand everything in today's lesson before we can get there.

Next topic: why some cats (including calicos) have white feet (or white feet, legs, and bellies).

Fishfrog said...

Is it because they stepped in white paint?

Matt said...

kitty cats! more genetics of fluffy kitty cats!

nell said...

Did you ever see the Pepe Le Pew where the cat gets paint on its back and looks like a skunk? That cat lacked an O gene but made up for it in latex. See how smart I sound!